Improve script robustness with set -euo pipefail

[rauldsl]

Description

Enable set -euo pipefail in the GPU Operator NVAIE installation script to improve robustness.
This ensures the script:

• Exits immediately on any command failure (-e)
• Detects use of unset variables (-u)
• Fails if any command in a pipeline fails (-o pipefail)

This change reduces the risk of partial or inconsistent deployments during installation.

Checklist

• No secrets, sensitive information, or unrelated changes
• Lint checks passing (make lint)
• Generated assets in-sync (make validate-generated-assets)
• Go mod artifacts in-sync (make validate-modules)
• Test cases are added for new code paths

Testing

Tested manually by running the script on a cluster with an existing GPU Operator namespace, verifying that:

• The script exits immediately if a required environment variable is missing
• The script stops if any kubectl or helm command fails
• Existing resources are handled correctly without partial creation

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[rauldsl]

Just refreshed the PR with a clean rebase and removed an unrelated commit.
The change now only includes the intended fix. Ready for review again, tks!!! /lgtm